Along with the development of functions of mobile phones, there have been cases where, when a function to erase a screen display such as a function to turn off power and a power saving function is performed automatically, a user of a mobile phone recognizes incorrectly that a failure has been occurred, resulting in such as requesting repair. Accordingly, a user interface which is easy to understand for a user was not being provided.
For this reason, users have been informed of the reason or the like of the erasure.
For example, patent citation 1 discloses a mobile communication terminal having: a function to report a low voltage warning before the output voltage of the power supply battery becomes low to a level where stable operation cannot be performed any more, and then turn off the power of the terminal itself; and a battery voltage detection means which detects the output voltage of the power supply battery, which comprises: an operation determination threshold value storage means for setting and memorizing a first operation determination threshold value for determining whether the power of the terminal itself should be turned off or not according to the output voltage of the power supply battery, and a second operation determination threshold value which is higher than the first operation determination threshold value for determining whether the power of the terminal itself should be turned off after reporting operation of a low voltage warning or usual waiting operation should be performed; an operation control means which detects the output voltage of the power supply battery using a battery voltage detection means when a turning-on of the terminal is requested, compares the detected output voltage and each of the operation determination threshold values, and controls operation determined by each of the operation determination threshold values according to the comparison result.
This mobile communication terminal operates as follows.
It is configured to comprise a function to report a low voltage warning before the output voltage of the power supply battery becomes low to a level where stable operation cannot be performed any more, and then turn off the power of the terminal itself, and a battery voltage detection means which detects the output voltage of the power supply battery, which comprises: an operation determination threshold value storage means for setting and memorizing a first operation determination threshold value for determining whether the power of the terminal itself should be turned off or not according to the output voltage of the power supply battery, and a second operation determination threshold value which is higher than the first operation determination threshold value for determining whether the power of the terminal itself should be turned off after reporting operation of a low voltage warning or usual waiting operation should be performed; an operation control means which detects the output voltage of the power supply battery using a battery voltage detection means when a turning-on of the terminal is requested, compares the detected output voltage and each of the operation determination threshold values, and controls operation determined by each of the operation determination threshold values according to the comparison result. Thus, it is possible to report to the user that the power has been turned on when a request for turning on of the power is given by a user after performing power-off following indication of low voltage alarm. Accordingly, complaints such as “Power not turned on” and the like after performing power-off following indication of low voltage alarm and unstable operation in a state of low battery voltage can be avoided.
That is, this mobile communication terminal notifies the user in the event that the power is turned on by the user after the power is turned off according to low voltage detection.
Patent citation 2 discloses a mobile communication apparatus having: an image photographing means; an image display means; a communication means which performs communication including an image between another party's communication device through a wireless line; and a battery which supplies electric power for operation to each of these means, which comprises: a power monitoring means which detects that the battery voltage has declined to a level not more than a predetermined value; and a control means which turns off power supply for at least one of the image photographing means and the image display means, when a battery voltage declining detection notice is received from the power monitoring means in a communicating state including an image with another party's communication device.
This mobile communication apparatus operates as follows.
It is configured to comprise an image photographing means and an image display means, and turns off a power supply to at least one of the image photographing means and the image display means when it is detected that battery voltage has been declined to a level not more than a predetermined value. Thus, a mobile communication apparatus which can save the consumption current of a battery and endure long hours of use as long as possible is realized.
Patent citation 3 discloses a power source switching circuit of a cellular phone operated by a battery having: a main battery which is usually used; a sub battery used as a reserve of the main battery; a voltage monitoring means which monitors an output voltage value of the main battery always, and outputs a switching signal when the output voltage value becomes not more than a predetermined value; and a switching means which supplies power to a logic circuit and a communication circuit from the main battery usually, and switches to power supply from the sub battery when a switching signal is received.
This power source switching circuit of this cellular phone operates as follows.
It is provided a main battery and a sub battery, and when the output voltage value of the main battery which supplies power usually becomes a predetermined value or less, it is changed to power supply from the sub battery. Thus, a charge for the main battery can be performed without suspending the function of the cellular phone.    [Patent citation 1] Japanese Patent Application Laid-Open No. 2001-053671    [Patent citation 2] Japanese Patent Application Laid-Open No. 2001-094500    [Patent citation 3] Japanese Patent Application Laid-Open No. 1993-244733